What is the meaning of Non-terminal_symbol?

5-letter words containing

• 5-letter words containing r

• 5-letter words containing b

• 5-letter words containing o

• 5-letter words containing e

• 5-letter words containing u

5-letter words starting with

• 5-letter words starting with e

• 5-letter words starting with o

• 5-letter words starting with l

• 5-letter words starting with n

• 5-letter words starting with k

5-letter words in the middle

• 5-letter words in the middle s

• 5-letter words in the middle n

• 5-letter words in the middle l

• 5-letter words in the middle p

• 5-letter words in the middle n

5-letter words ending with

• 5-letter words ending with i

• 5-letter words ending with z

• 5-letter words ending with n

• 5-letter words ending with e

• 5-letter words ending with e

5-letter words excluding

• 5-letter words excluding g

• 5-letter words excluding o

• 5-letter words excluding i

• 5-letter words excluding e

• 5-letter words excluding n